There are two QL Wikis that I know of – both of which cover very different areas.
Rich Mellor’s QL Wiki at http://www.rwapadventures.com/ql_wiki/ contains a wealth of information on software and hardware, books, QL history, platforms, traders, personalities and all sorts of things! It’s even possible to sign up with Rich to edit and add pages if you’d like to add and update information on there. The QL Wiki is a real treasure trove of information about the QL and its software – it lists most if not all the commercial software ever released for the QL, just what the avid collector would need. For those who don’t (yet!) know him, Rich Mellor is a QL trader of long standing, who is also the driving force behind the SellMyRetro.com auction site
Norman Dunbar’s QL DocuWiki has a very different content. Located at http://www.qdosmsq.dunbar-it.co.uk/doku.php it concentrates on QL programming and operating system information. It is also possible to sign up to work on and contribute to this one, although you will have to ask Norman to sign you up (it used to be possible to subscribe yourself to it, but he had huge problems with bots attacking the site and removed that facility in 2013). The wiki is packed full of some very useful information.